Regulation of T cell responses plays a primary role in determining the outcome of auto-immune disease, the development of tumor immunity, and graft survival following transplantation (Bluestone, et.al. Annu, Rev. Immunol. 1996, 14, 233-258.; Kuchroo, et. al. Crit. Rev. Immunol. 1998, 18, 389-418.; Guinan, et. al. N. Engl. J. Med. 1999, 340, 1704-1714.; Abrams et. al. J. Exp. Med. 2000, 192, 681-694). These immune responses are controlled by the interaction of molecules on T cell and antigen presenting cell surfaces. Activation of T cells requires two signals, an antigen-specific signal delivered through T cell antigen receptor, and a second co-stimulatory signal. This co-stimulatory signal dictates the outcome for T cells through the binding of B7-1 and B7-2 expressed on antigen presenting cells to CD28 and CTLA-4 on T cells. CD28 engagement by B7-1 or B7-2 amplifies T cell receptor signaling and stimulates production of cytokines required for T-cell proliferation. On the other hand, CTLA-4 engagement by B7-1 or B7-2 down regulates the immune response (Allison, et. al. Nature 1992, 356, 607-609.; Bluestone, et. al. Immunity 1994, 1, 405-413.; Thompson, et. al. Science 1995, 270, 985-988). In experimental disease models, altering these co-stimulatory signals has profound effects on immunity. Blocking B7/CD28 interactions with monoclonal antibodies or soluble receptors results in immunosuppression and enhanced allograft survival, while B7/CTLA-4 blockade results in enhanced anti-tumor immune responses (Larsen, et. al. Nature 1996, 381, 434-438). Consequently, agents, such as small molecules, which act as inhibitors of cell-cell interactions may be useful in the development of effective immunomodulatory medicines.
Therefore, it is an object of this invention to provide compounds which are useful as immunotherapeutic agents in the treatment of transplant rejection, autoimmune disease or graft vs host disease.
It is another object of this invention to provide therapeutic methods and pharmaceutical compositions useful for the treatment of transplant rejection, autoimmune disease or graft vs host disease.
It is a feature of this invention that the compounds provided may be used to further study and elucidate the interactions of B7-1 with the CD28 receptor.
These and other objects and features of the invention will become more apparent by the detailed description set forth hereinbelow.